What to read after Incarceron?

A New York Times Bestseller -- Incarceron is a prison unlike any other: Its inmates live not only in cells, but in metal forests, dilapidated cities, and unbounded wilderness. It has been sealed for centuries, and only one man, legend says, has ever escaped. Finn, a seventeen-year-old prisoner, believes he came from Outside Incarceron. He's going to escape, even though most inmates don't believe that Outside even exists. Then Finn finds a crystal key and through it, a girl named Claudia.